Cataract surgery, the most commonly performed procedure in the United States, has undergone substantial technologic improvements over the past 20 years. One would anticipate that the smaller wounds, shorter operative time, and more rapid visual and ambulatory recovery would be associated with a reduction in the rate of postoperative endophthalmitis, perhaps the most significant operative complication. We show preliminary research that strongly suggests that the rate has been increasing over the past decade and that age and black race are important risk factors. The literature on the epidemiology of endophthalmitis is largely limited to small and regional studies. These suggest that surgical factors such as the location (ie. corneal vs scleral) and closure (ie. use vs non-use of stitch) of the wound may be important as well as intensity and timing of perioperative antibiotic use. We propose to ascertain nationally representative rates of acute endopthalmitis following cataract surgery by identifying and verifying cases of endophthalmitis ascertained from Medicare data files. We will then try to identify patient and surgical risk factors for endopthalmitis in a population-based case-control study by examining potential risk factors in 392 cases and 1176 controls drawn from the same Medicare base. The investigators hope to identify factors that can be modified to lower the rate of endopthalmitis and to provide information that would facilitate planning for future interventional trials. [unreadable] [unreadable]